An exhaust hood is a device including a mechanical fan that is installed above the stove or cooktop in the kitchen. It removes airborne grease, combustion products, fumes, smoke, odors, and steam from the air by evacuation of the air. In most exhaust hoods, a filtration system removes grease and other particles. Although many exhaust hoods exhaust air to the outside, some recirculate the air to the kitchen. In a recirculating system, filters may be used to remove odors in addition to the grease. Commercial exhaust hoods may also be combined with a fresh air fan that draws in exterior air, circulating it with the cooking fumes, which are then drawn out by the hood.
U.S. Pat. No. 6,851,421 B2 describes an exhaust hood, which captures and contains a thermal plume by defining a vertical curtain jet. In one embodiment, vertical and horizontal jets can be combined to augment capture and containment. The horizontal jet pushes the plume toward the exhaust vent at the side of the hood and creates a negative pressure field around the forward edge of the hood which helps containment. The hood uses air nozzles in the form of small round holes positioned along the front of the exhaust hood. The nozzles are spaced apart from each other such that they form individual jets which combine into a curtain jet. However, on the one hand, the vertical air curtain may be efficient only for certain hood geometries and proves less efficient for others; on the other hand, the vertical air jets can be annoying for kitchen personnel who have to work below the hood all day.